in dichloromethane byproducts: SO2, N2; stirring mixt. of Te-compd. and SbCl5 (molar ratio 2.1:1.5) in abs. CH2Cl2 at -80°C in a sealed tube (12 h); filtration of pptn. in absence of air and moisture, washing (CH2Cl2), concn. of combined filtrates by removal of solvent in vac. to half of vol., crystn. after few weeks;